1. Core Mission and Aims COPD is a preventable and treatable disease state characterised by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and is associated with an abnormal inflammatory response of the lungs to noxious particles or gases, primarily caused by cigarette smoking. Although COPD affects the lungs, it also produces significant systemic consequences that may have important clinical impact. Thus, the characterization of subjects with COPD must move beyond the very narrow spirometric classification of lung function and include such metrics as anthropometrics, nutritional status, questionnaire-based assessments of both symptoms and disability, and image-based measures of airway and parenchymal disease. Phenotype in this proposal is defined as "the outward manifestations of patients with COPD;anything that is part of their observable structure, function, or behaviour(l)." The goal of this Clinical Phenotyping Core is to augment the very strong genetic, epidemiologic, and basic science components of this program project by building two cohorts of subjects that have undergone detailed clinical evaluation and quantitative image analysis of the lungs. One of these cohorts ("Lung Tissue Population") will have surgically explanted lung tissue;the other cohort ("Bronchoscopy Population") will have bronchoscopically obtained samples of the lung. Based upon their broad expertise, tlie Clinical Phenotyping Core will provide robust measures of disease in these subjects for use in all three of the PPG Projects.